1. Field of the Invention
The present invention relates to a combination terminal, formed with a plurality of plate terminals bound together and coupled to a plurality of electric wire terminals by pressure-welding, so that the electric wire terminals are collectively connectable in automotive equipment or the like.
2. Related Art
When a plurality of plate terminals used for automobile ground wires and the like are bound together before being coupled to one place, the conventional practice is to join securing members provided at the front ends of the respective terminals and to fix the combination to a desired portion of a car body with a bolt by concentrically superposing securing holes. Clamping members are provided at the rear ends of the respective terminals and are used for pressure-welding electric wire terminals. Since these clamping members are three-dimensional in contour, they tend to interfere with each other during the securing operation, thus making it extremely difficult to combine the plate-like securing members precisely. The drawback is that the function of the electric wire terminal may be impaired by the deformation of the base of the securing member because of its buckling, for example, and by the space produced between the securing members.
In order to obviate the aforementioned drawback, there have been proposed combination plate terminals 1M and 1N consecutively incorporating respective joints 3m and 3n as shown in FIGS. 17 and 18. It is however needed to couple electric wires 4 that have been clamped together to the respective joints 3m and 3n of the combination plate terminals 1M and 1N. Consequently, difficult operations are required, including moving a number of set electric wire elements to a desired position and pressure-welding the plurality of electric wires to one plate terminal while arranging them in order before actually securing the terminal to equipment.
Japanese Utility Model Publication No. 12543/1988, for example, discloses a combination terminal which is intended to avoid such complicated work as noted above through the steps of coupling a plate terminal to each set electric wire element beforehand and joining two plate terminals mounted on a conveyor line instantly in the process of manufacturing set electric wires. More specifically, a plate terminal 1P comprises, as shown in FIGS. 19 and 20, a rectangular securing member 2p with a securing hole 5 for receiving a clamp bolt therethrough, the securing hole 5 being provided in the central part of a base plane 6p, and a joint 3p which is U-shaped in cross section, the joint 3p being incorporated with the securing member 2p and protruded outwardly. A retaining plane 7p is set opposite and parallel to a tongue-like retaining plane 8p along the longitudinal direction of the joint 3p with the securing hole 5 in the base plane 6p therebetween. The retaining planes 7p and 8p are formed so that each of them is stepped up by the thickness of the base plane 6p. The retaining plane 7p is provided with a fitting hole 9p, whereas the retaining plane 8p is provided with a lock pawl 10p thereon.
As shown in FIG. 21, further, the two plate terminals 1P, 1R thus arranged are placed one upon another as shown by a chain line in such a manner as to join the securing members 2p, 2r back to back. Subsequently, the securing member 2r is slid in the direction of an arrow so as to superpose the retaining planes 7p, 8r of the plate terminals 1P, 1R, and the retaining planes 8p, 7r of the plate terminals 1P, 1R, respectively. Then the two plate terminals 1P, 1R are integrally combined together when the lock pawls 10r, 10p engage with the respective fitting holes 9r, 9p.
However, because plate terminal 1P has the fitting hole 9p bored in the retaining plane 7p and the lock pawl 10p cut upward, its strength is lowered because the sectional areas of the retaining planes 7p, 8p have been reduced. Moreover, the difference in level between the retaining planes 7p, 8p and the base plane 6p also results in reducing the terminal's bending strength. Consequently, there is the possibility that the retaining planes 7p, 8p and the securing member 2p in combination will be deformed when they are put in place. The resulting dimensional distortion may invite failure in mating the plate terminals 1P, 1R or cause the terminals to be easily disconnected.
Since there are two places where the lock pawls mate with the respective fitting holes, there may arise a problem in that backlash ensues after the plate terminals 1P, 1R have been joined together, thus causing the terminal to be easily dislocated, for example.
Although it is preferable for the plate terminals 1P, 1R to be readily joined together with moderate force of fitting the lock pawls into the respective fitting holes, greater holding strength is desired after they have been joined together. If, however, an attempt is made to reduce the force of insertion by decreasing the size of such a-lock pawl, for example, its holding strength will be decreased. If, conversely, increasing the holding strength is attempted, the force of insertion will also need to be increased.
In some cases, a combination of applicable electric wires different having different diameters and two kinds of plate terminals having different plate thicknesses are used. In such a case, the following problem is posed.
The clamping contour of a combination terminal depends on the diameter of the electric wire; small diameter electric wires fall in a range of 0.5-2.0 mm.sup.2 and large diameter electric wires fall in a range of 2.0-5.0 mm.sup.2. Normally, a plate material 0.8 mm thick is uniformly used to satisfy the clamping performance of the large diameter wire. However, when the plate terminal 0.8 mm thick is used to clamp electric wires having a diameter of as small as approximately 0.5 mm.sup.2, the weldability remains unstable and some of the small diameter electric wires may slip out of the plate terminal.
As shown in FIG. 22, if a plate terminal T 0.8 mm thick and a plate terminal U 0.6 mm thick are used for large- and small-diameter electric wires, spaces 23 will be formed between the base plane 6u of the thin-wall plate terminal U intended for the small diameter electric wires and the contact surface 21a of a bolt 21, and between a retaining plane 14u and the contact surface 22a of a securing member 22, respectively. Due to these spaces 23, the pressing force of the clamp bolt 21 is not transmitted smoothly and this may cause backlash and failure in preventing the electric wires from slipping out after they have been clamped.